In certain vehicles, a cast subframe is provided to the rear of a power plant (an engine/transmission unit) in the vehicle body and suspension arms are supported on left and right sides of the subframe. The subframe has a front wall sloping upward toward the rear of the vehicle body.
The suspension arms have a front connecting part connected to a leading-side part of the subframe, and a rear connecting part connected to a trailing-side part of the subframe. Consequently, loads inputted to the suspension arms are transferred to the leading-side part or the trailing-side part of the subframe via the front or rear connecting part of the suspension arms.
The loads transferred to the leading or trailing-side part of the subframe are transferred to the side parts of the subframe between the leading- and trailing-side parts (see JP-A 2012-136195, for example).
In the subframe of Patent Document 1, a front wall is formed sloping upward toward the rear of the vehicle body. Consequently, a join part (“parting line” below) of a casting mold (a fixed mold and a movable mold) used when the subframe is cast is positioned in a bottom part of the subframe. A crease mark (i.e. parting mark) of the parting line is formed in the bottom part of the side part of the subframe due to the parting line being positioned in the bottom part of the subframe. Due to the parting mark being formed in the bottom part of the subframe (the side parts), it is thought that stress concentrates in the parting mark when a load are transferred from the suspension arms to the side parts of the subframe.
Thus, the subframe needs to be made reliably strong, in which regard there is scope for improvement.